The present invention generally relates to mattress foundation structures and more particularly to a non-coil spring and spring assembly used in a box spring structure.
A variety of bent wire springs or so called modular springs have been developed to replace coil springs in box spring assemblies in which a grid frame is connected to a rigid base frame. Such box spring assemblies are commonly used for supporting mattresses. Bent wire springs have certain advantages over conventional coil springs as they provide a desirably stiff foundation, contain a reduced amount of wire, have a prolonged service life and are easier and less costly to manufacture.
One prior bent wire spring module over which the present invention is an improvement is disclosed by Hagemeister in U.S. Pat. No. 4,828,233. This patent discloses a bent wire spring module having means for locking the upper end of the spring to a grid wire without the need for fasteners such as sheet metal clips and without the need for forming deviations in the grid wires as was common practice in the prior art. The locking means disclosed in this Hagemeister patent includes support wires each being connected to downwardly angled locking wires by a curved connecting portion in the wire. The distal ends of the locking wires are connected by a curved portion which is angled upwardly with respect to the locking wires. The modular bent wire spring is placed over a wire of the wire grid such that an inside surface of the curved connecting portion abuts against the grid wire.
Although the bent wire spring module of Hagemeister has been an improvement over past designs of such springs, design features are contemplated in the present invention which improve manufacturing efficiency and facilitate easy assembly of the modules with a wire grid.
Accordingly, it has been one object of the invention to provide a bent wire spring module having a locking mechanism which eliminates the need for forming deviations in the grid wires or using separate fasteners but also significantly improves manufacturing efficiency associated with the module.
It has been another objective of the invention to provide a bent wire spring module which is easier to assemble into a spring assembly.